Otherwise ingested data will not be processed because Beam job is not ready

* create cassandra store for registration and ingestion

  * Downgraded Guava to 25
    * Beam 2.16 uses Cassandra 3.4.0 (So we cannot use Cassandra 4.x which shades Guava)
    * Cassandra 3.4.0 uses Guava version 16.0 but has a compatibility check to use a different class when we use version > 19.0.
    * Guava version 26 (version previously used) has breaking change to method used in compatibility check in Cassandra's dependency, hence version 25
  * Using Cassandra's internal field 'writetime' to handle out of order arrivals. When older records where the primary key already exist in Cassandra are ingested, they are set as tombstones in Cassandra and ignored on retrieval.
    * Aware that this way of handling out of order arrival is specific to Cassandra, but until we have a general way to handle out of order arrivals we need to do it this way
  * Cassandra's object mapper requires stating table's name along with @table annotation
    * table_name is still part of CassandraConfig for use in serving module
    * if user registers CassandraConfig with a different table name other than "feature_store", this will throw an exception

* add cassandra serving service

  * Abstracted OnlineServingService for common implementation of online serving stores
  * Complete tests remain in RedisServingServiceTest while Cassandra tests only contain basic tests for writes, and some other implementation specific to Cassandra

* update documentation to reflect current API and add cassandra store to docs

* add default expiration to cassandra config for when featureset does not have max age

* docs update, spotless check, and bug fix on cassandra schema

* Use Nexus staging plugin for deployment (#394)

* Use Nexus staging pluging for deployment

* Fix Javadoc error

* Hard coded parent version as variable substitution is not supported

* Introduce datatypes/java module for proto generation

Rather than the Maven protobuf plugin running on the same symlinked
definitions in several Java modules, localize this process into one
module that the others depend on.

This provides a single module that can be depended on by third-party
extensions with the bare minimum of dependencies.

Also removes proto files that are no longer used.

* Java SDK release script (#406)

* Use back revision variable in pom.xml
So user or CI system can easily override revision from external sources such as Git tag name

* Add flatten maven plugin
This plugin is useful during deployment so the final pom is resolved without parent dependency, i.e. we do not necessarily need to upload parent library

* Increase versions for maven source,javadoc,spotless plugins
So it has newer features and more fixes

* Add gpg-plugin needed to sign releases

* Use oss configure for flatten plugin, add developers info in pom.xml (required for releasing library

* Add publish-java-sdk script

* Add more logs to publish-java-sdk.sh

* Add ProwJob publish-java-sdk

* Use GPG_KEY_IMPORT_DIR variable

* Update revision in pom.xml to 0.4.2-SNAPSHOT

* Publish datatypes/java along with sdk/java

Co-authored-by: Khor Shu Heng <32997938+khorshuheng@users.noreply.github.com>
Co-authored-by: David Heryanto <david.heryanto@hotmail.com>

v0.3.6 was tagged and 0.3.x development has moved forward. See #442

* Fail formatting check before tests execute

By default, the spotless Maven plugin binds its check goal to the verify
phase (late in the lifecycle, after integration tests). Because we
currently only run `mvn test` for CI, it doesn't proceed as far as
verify so missed formatting is not caught by CI.

This binds the check to an earlier phase, in between test-compile and
test, so that it will fail before `mvn test` but not disrupt your dev
workflow of compiling main and test sources as you work. This strikes a
good compromise on failing fast for code standards without being _too_
nagging.

For the complete lifecycle reference, see:
https://maven.apache.org/guides/introduction/introduction-to-the-lifecycle.html

* Apply Spotless formatting

Hopefully for last time as a bulk operation, after 6363540.

* Make dependency:analyze run clean on datatypes-java

* Remove stale dependencies from ingestion

Unused according to `mvn -pl ingestion dependency:analyze`, and tests.

We had a recent bump of hibernate-validator with a CVE fix (#421) that I
was looking to backport, and it turns out it's not used anymore anyway.

* Release v0.3.7

* Remove SNAPSHOT from e2e tests

* Find jar version from Maven